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April 12, 1966 R TEUCHER 3,246,079

METHOD AND MEANS FOR THE PREPARATION OF PRINTING FORMS, ESPECIALLY OFINTAGLIO PRINTING SUR'FACES Flled Oct. 2, 1961 5 Sheets-Sheet l MIRO@ N.mt

April 12, 1956 R. TEUcHl-:R 3,246,079

METHOD AND MEANS FOR THE PREPARATION OF PRINTING FORMS, ESPECIALLY OFINTAGLIO PRINTING SURFACES Filed Oct. 2, 1961 5 Sheets-Sheet 2IHIIIIIIIIH PULS GENE/9,4 T01? VOL 7465 SUP/ZY ANO CA/I'OL SYSTEM Mcm/MPUMPS Jn vena r: fw? MJ Maya.

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METHOD AND MEANS FOR THE PREPARATION 0F PRINTING FORMS, ESPECIALLY OFINTAGLIO PRINTING SURFACES Filed Oct. 2. 1961 5 Sheets-Sheet 5 Fig.. 3

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METHOD AND MEANS FOR THE PREPARATION OF PRINTING FORMS, ESPECIALLY OFINTAGLIO PRINTING SURFACES Filed Oct. 2. 1961 5 Sheets-Sheet 4 Fig. 4

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METHOD AND MEANS FOR THE PREPARATION OF PRINTING FORMS, ESPECIALLY OEINTAGLIO PRINTING sURFACEs Filed Oct. 2. 1961 5 Sheets-Sheet 5 Fig. 5

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United States Patent O 3,246,079 METHD AND MEANS FOR THE PREPARATEDN FPRNTING FRDIS, ESPECIALLY 0F IN- TAGLI() PRJNTING SURFASES RudolfTeacher, Sprendlingen, Oifenbach, Germany, as-

signor to Era European Rotogravure Association, Basel, SwitzerlandlFiled Oct. 2, 1%1, Ser. No. 142,407 Claims priority, applicationGermany, Oct. 22, 1960, T 19,174 Claims. (Cl. Mii-6.6)

Printing forms are made mainly by the photo-chemical process. Owing tothe large number of operations required, however, thisl process istime-consuming and requires considerable experience in the art and alsogreat skill. The result always depends decisively upon the individualtreatment of the separate operations.

It is also known to make printing forms by physical machining methods.These include a known process wherein the required material removaloperation is carried ont by a stylus controlled by the original to beIeproduced. Another proposal provides for removal of the material byspark discharge, an electrode being moved over the surface of thematerial of the printing form. All these processes entail a certainamount of ine-rtia as a result of the mass of the stylus or electrodesand are therefore relatively slow in operation.

In another known method, use is made of the materialremoving propertiesof an electron beam. An electron beam is sluiced through a pressurestage system into .the working chamber, which is under atmosphericpressure, and continuously removes material from the printing block,form or plate material therein, the amount of material being removeddepending upon the intensity of the beam. The intensity is controlled bythe light-dark scale of the original to be reproduced.

Another known process utilises the material-removing properties of anelectron beam for the production of small spheres.

A method of treating materials by means of a beam of charged particlesis also known, for example, to make holes in a plate.

ln another known method and apparatus for material machining by means ofa charge-carrying beam, the pattern of a printed circuit is developed bymeans of a chargecarrying beam. The original is photographed by atelevision camera and the deflection signals serving to control thetelevision pick-up tube scanning beam serve at the same time for thesynchronous detiection of the chargecarrier beam over the object to bemachined, and the video-signals furnished by the television camera serveto control the intensity of the charge-carrier beam` meeting the object.

Finally, a method is known wherein material is removed and thus printingforms, blocks or plates are produced by spark discharge between apointed electrode and the surace of said form, block or plate. It isalso pos-sible to use corpuscular radiation to give the surface ofmetals the character of a printing form, block or plate. The latter twomethods have not hitherto been used in practice.

The main object of the invention is to provide methods of producingprinting forms, more particularly intaglio forms, by means of electronbeams, these methods being intended to give a considerable improvementof the lightdark values and hence improved quality of the reproduction,in the production of printing forms from singleor multi-colouredoriginals, by the defined removal of material by an electron beam.

A further object of the invention is to provide methods and apparatusfor the production of printing forms, blocks or plates `from singleormulti-coloured originals,

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wherein the printing forms can be made in a significantly shorter timethan has been possible with the previous stylus processes or chemicaletching processes.

A further object of the invention is to provide methods of the aforesaidkind wherein any required correction may be provided in simple manner inthe transmission between the original and the printing form, block orplate, in order thus to obtain any required modilication of the form,block or .plate in comparison with the original.

A further object of the invention is to provide methods and apparatuswhereby a very uniform and required shaping of the individual cells lcanbe achieved, in other words the quality of the cell-s can be improved,through a removal of surace material by means of an electron beam.

A further object of .the invention is to provide methods and apparatusof the aforesaid kind whereby known processes are simpliiied.

A further object of the invention is to make printing Iforms, usingelectron beams, a speci-al control system being used to ensure `that theindividual printing elements are depicted sharply .and in accordancewith the original, with an adjustable control characteristic.

A further object of the invention is to prov-ide methods and apparatusof the aforesaid kind whereby any required storage of ythe pulsesrecorded from the original and reproduction at any required time and atany required location are possible for the production of printing forms,blocks or plates.

The principle on which the invention is based is that it is pos-sible toscan coloured or black and white originals with or without a screen andto use the electrical currents or voltages which are proportional to thegrey or colour values of the original to control mechanical, electricalor electronic components which remove from the surfaces of the printingstock Imaterial volumes of material which, taking into account theprinting ink, are in a denite relationship to the scanned grey or colourvalues of the original.

In the method according to the invention, for the production ofprint-ing forms, use is made of electron bea-In pulses which meet eachindividual surace elemental area of the form mate-rial one or lmoretimes, it being possible to control the intensity of the pulses, thenumber of pulses per element of surface area, their duration and theirfocussing sharpness, electrically or magnetically by means of thelight-dark value which is scanned photoelectrically from thecorresponding surace elemental area of the original. The resultantdilTe-rential removal of material from the different surface elements ofarea gives rise to a printable relief image of the original on aprinting plate, a printing cylinder, or the like.

It is `accordingly within the scope of .the invention to inilnence theprinting stock material as required by influencing the beam intensity,the focussing, pulse duration and the time between two pulses. It isalso within the scope of the invention to vary the shape, depth andcontour of the printing form elements by one of the said steps or by acombination of said steps. It is further within the scope of theinvention to use appropriate masks, which are reproduced on a reducedscale on the printing form material by the electron beam, so as toobtain individual cells of a required shape, for example a square ordiamond shape, while the depth off the cells and their surace form canbe inuenced by the steps explained hereinbefore.

According to one embodiment, the method according to the invention maybe performed in practice by optically scanning each individual elementof an original which, for example, may comprise singleor multi-colourmatter, by means of a scanning device, converting the scanned values ina photo-electric cell into yvoltage or current values corresponding tothe brightness of the original, dividing up into individual fixed pulsesthe resultant signals which are in the form of voltage fluctuations, andfeeding the resultant pulses, after further amplification if required,to a high-voltage electron gun, and using these pulses to control theelectron beam in the form of pulses.

According to a practical embodiment of the invention, it is possible tofeed the voltage `fluctuations which, for example, are produced by aphoto-electric cell according to the brightness values, to a pulsegenerator which operates in lthe manner of a chopper and which furnishesthe pulses which are to 'be converted, the .amplitude of theseindividual pulses being directly proportional to the light and darkvalues or fluctuations of these values in the original. The furtherconversion of the resultant pulses which correspond to the Abrightnessvalues of the original can be performed in various ways according to theinvention.

According to one embodiment of the method of the invention, this may becarried out electrically, the pulses produced in the pulse generatorbeing superimposed on the carrier Wave for emission of 4the latter atthe reception station, which is at high voltage.

According to `a further embodiment of the method of the invention, thepulses proportional to the brightness of the original may be `fed to acathode-ray oscillograph, and the brightness of the picture elementproduced there is thus controlled. By means of an electrically separatereceiver at high-voltage on the reception side these pulses can bereconverted to electrical pulses `and fed to the highvoltage electrongun.

According to Ia further embodiment, the invention may also be performedby wireless transmission, directly to the high-voltage electron gun, ofthe current values which are scanned from the original by the scanningdevice and which fluctuate according yto the brightness, said currentvalues continually controlling the intensity of the electron beamproduced at the electron gun.

In performing the methods of the invention explained hereinbefore it ispreferable to `mount the original on a cylinder and rotate this cylinderat a constant speed of revolution and to advance -it slowly per unit oftime so that a fixed beam of light scans the original in a spiral havinga very small pitch, the speed of revolution of this original naturallbeing in synchronism with the speed of revolution of the printing format the reception station.

In a further embodiment of the invention, a plane original may be used,the said plane original ybeing moved beneath a fixed beam of light withlinewise scanning of the original.

According `to a further embodiment of the invention, the original to bereproduced may oscillate Vat a required frequency so that the planeoriginal can be scanned according to any required pattern. In this case,of course, the scanning station or the original at the reception endmust be moved correspondingly.

According to a further embodiment of the method according to theinvention, where a rotating cylinder is used for the original to `bereproduced, it is preferable to `rotate a pulse generator device insynchronism with the said cylinder, by means of which pulse generatorthe signals coming from the scanning device in the form of voltagefluctuations, as already explained, are split up into individual pulseswhich are fixed as to time and location by the printing cylinder and thevalue of which is proportional to the brightness of the original to bereproduced.

According to a further embodiment of the invention, it is possiblepositively to couple the drive for the cylinder of the original to thepulse generator mechanically at the reception station so that the pulseswhich are fed at the lreception station to an electron-optical system tobe explained hereinafter are absolutely in synchronism with the pulsesproduced in the pulse generator, without any correcting device beingnecessary for the purpose. This embodiment is particularly simplebecause the position of the pulses with respect to their location on theprinting cylinder is definitely fixed from the outset. The pulserepetition frequency of the pulse generator is thus determined lby thespeed of `revolution of the printing cylinder at the original scanningstation.

The tmethod of the present invention can be modified by 'controlling theelectron beam by the production of square pulses by a pulse generatordisc or equivalent element rotating synchronously with the printingcylinder, the said square pulses being applied in the same IWay to thehigh-voltage side of the electron-optical system as the pulsescorresponding to the `brightness values of the original. Additionallyaccording to a further embodiment of the invention, `for this purpose itis possible for the electron-optical system to incorporate a beam tube,to one control electrode of which the square pulses are applied to openor interrupt the beam, `and to feed the fluctuations corresponding tothe original brightness values to a second control electrode, Iwhichfluctuations in the rhythm of the pulses produced lby the pulsegenerator interrupt the electron beam, the intensity of `which variesaccording to the brightness values of the original.

According to one feature of the invention, a variation of the pulseaction can be obtained by variation of the focussing, and this iseffected, for example, by means of control electrodes. Assuming that anelectron beam contains a certain number of electrons and hence has acertain electron density, variation of the voltage at the controlelectrodes of the electron-optical system will give a variation in thecurrent density of the electron beam and this may be effected firstly byvarying the beam bunching and secondly by varying the current magnitude.

It is within the scope of the invention to obtain a variation in thedepth of the cells by the above-explained steps as a consequence of thescanned pulses or the number of pulses. The cell diameter can be variedat the same time by this pulse control, so that the shape and/ or thediameter of the cell also varies as a result, whereby the volume of thecell can also be varied as required.

This embodiment has the particular advantage that as a result of thebeam focussing all the metal is vaporised instantaneously and thisavoids the disadvantage that, for example, Where use is made of a singlerelatively long pulse there might be insufficient intensity at the edgesof the beam, due to poor focussing of the latter, to vaporise all themetal instantaneously, so that at the edges of the cell melting zonesform which result in a crater edge projecting from the plane of theprinting form, block or plate. Thus since according to the invention anyrequired focussing can be used for the electron beam and the low-energyregions of the beam which are not adequate for melting are masked out bya suitable mask, the advantage of instantaneous vaporisation of all thematerial is obtained without any craters being formed; at the same time,as already indicated, cells of any desired shape may be made inaccordance with the manner of focussing.

The top limit of the pulse duration may if desired be aboutmicroseconds, but operation is preferably carried out below that value.The energy density in the beam cross-section should then be in theregion of at least 10,000 kw. per sq. cm. in order to obtain asufficiently deep engraving.

From the electronic standpoint, there is no upper limit to the engravingspeed which would be limited only by the mechanical movement of theprinting support. When rotating printing supports are used, speeds of30,000 printing elements per second can be obtained without difhculty.

According to a further embodiment of the invention, the intensity of theelectron beam may also be varied by varying the pulse height. It isassumed that a square wave voltage maintained over a certain period isapplied to one control grid. By varying the current it is possible toobtain variation in the energy and hence a variation in the intensity ofthe pulse. In other words, the amplitude of the square Wave voltage canbe varied and thus a variation of the energy content of an individualpulse from the original is obtained as a function of the control voltageapplied. With the present embodiment of the invention this can beeifected by varying the voltage in the Wehnelt cylinder of theelectron-optical system. In addition, the energy content of anindividual pulse can be varied by a second control electrode by the factthat even when fully opened by this pulse the magnitude of the electrodebeam current is limited by the potential applied to the second controlelectrode.

According to a further embodiment of the invention, a variation of thepulse intensity can be obtained by varying the duration of the squarewave pulse.

According to the invention it is also possible to obtain a variation byvarying the time between two control pulses. This variation has nodirect iniiuence on the shape and size of an individual puise but itdoes vary the number of cells in the printing form, for example reducessuch number, when the time between two pulses is increased.

Finally, according to the invention it is possible to obviate any errorsin the original or vary the entire character of the original matter bysuitable choice of transmission of the brightness values scanned fromthe original to the electron beam pulses used for engraving. Bycharacter of the original matter in this context, for example, is meantthat contours are intensied, contrasts increased, and so on. Accordingto the invention, this can be achieved by varying the amplification,more particularly by the use of non-linear amplifier elements, and canbe carried out at any required stage of the transmission of the scannedbrightness values or of the brightness values converted into electricalpulses.

According to a further embodiment of the method according to theinvention, colour separations may also be made from coloured originals,and to this end, according to one embodiment of the method of theinvention, a coloured original is split up into three images eachcontaining their colour separations. With the photomechanical etchingprocess conventional today in the production of printing blocks it isnecessary first to make three colour separations from the colouredoriginal, these separations containing the engraving values according tothe individual colour components. These colour separations are then usedto make the individual blocks required for the individual colouredprint. The invention avoids this detour using at least three colourseparations, since it enables the coloured original to be scanned by abeam of light and thisv beam of light to be converted directly into thecorresponding density values by means of colour separation filters. Thecorresponding number of colour cylinders can then be effected directfrom the original simultaneously by control of a corresponding number ofengraving devices, the remarks made hereinbefore with respect to theyblack and white original again applying as regards apparatus. It istherefore only necessary to provide on the reception side acorresponding number of electronically operating en- `graving devicesand then the printing forms can be used directly in the printingprocess.

As an example, the above-explained method of the invention may beperformed in practice as follows:

It will be assumed that a coloured transparency has to be reproduced byprinting processes. The original is clamped for example, on a cylinderand its colour values are scanned by means of a scanning device which,for example, may consist of a light source and one or more photoelectriccells. The beam of light originating from the light source is projectedin the form of a dot on the surface of the original, passes through itand on the light reception side is split up into three identical imagecomponents, for example, by way of a multiple prism. In thephotoelcctric cell circuits, therefore, three voltages having differentuctuations according to the colour values are obtained and can in turnserve to control three engraving devices.

The three component beams are each scanned by a photoelectric cellthrough the medium of a colour separation filter, and from each point ofthe coloured original three output voltages are obtained which areidentical to the photographic grey rvalues of the corresponding pointsof the colour separations. The three voltages are then fed, for example,to three computers and colourcorrected electronically by methods knownper se. Component vo-ltages of the three pulses are also fed to anothercomputer which `in turn calculates ythe black separation value of thepoint of the original in question.

'The four pulse sequences obtained in this way now serve to control fourelectron beams which in turn engrave the four printing forms, blocks orplates.

It also comes within the scope of the invention to allow a plurality ofelectron-optical systems to operate in parallel from a single original,in a similar manner to that used in splitting up the colour of acoloured original, the pulses derived from the original being fed to aplurality of electronically operating engraving heads, so that it `ispossible to obtain printing `forms from a single original at a pluralityof places which, if required, are situated very far apart.

By the interposition of suitable means between the scanning unit and theengraving unit a storage method may be adopted to enable the scannedmatter to be recorded, for example, in the form of a magnetic tape. Themagnetic tape can then be used to control an electron-optical systemeither subsequently or after a relatively long period of storage.

By varying the speed of ythe magnetic tape during the recording orengraving and by appropriate control of the mechanical lateral movement,an image on an enlarged or reduced scale in relation to the original maybe produced on the printing material.

In addition to the advantage-s as explained, the invention has the basicadvantage that apart from the production of cells without any craterformation it is possible to produce perfect printing forms fromoriginals in a much shorter time than was possible hitherto. Taking anormal etching process as basis, it may be stated that the period fromthe original up to the completed printing cylinder is about 8 to l0hours using such a method, while when the method according to theinvention is used only a fraction of this time is required from theoriginal to the completed printing cylinder. A very considerable savingof Itime until the printing cylinder is ready is therefore obtained withthe method according to the invention.

By Way of example, taking as a basis the production of 30,000 printingelements per second with a 70`screen, a printing cylinder, block orplate of the size of 1 sq. metre can be made in a period of about 30lminutes.

Particularly in printing technology the invention will permit of otherbasic indirect advantages inasmuch as the considerable saving in timewill enable printing toy be carried out up to the very minute, i.e. itis possible to make printing cylinders from originals which werereceived at the editorial office just a relatively short time before thebeginning of printing.

As already explained, according to the invention it is preferable to usea fixed scanning beam and a moving original and/or a moving printingform, block or plate. It comes within the scope of the invention tokeep` the original and the printing form stationary and to move .thescanning beam and electron beam in relation thereto in a manner knownfrom the television art, in which case, of course, the two beams must becontrolled in synchronism.

The scanning movement of the scanning beam and of the electron beamwhich, in particular, will be a linewise movement, need not be explainedin detail here since the means are known to those versed in the art. Theconventional line scanning method or alternatively the interlacedscanning method may be used. Where use is made of originals in the formof a cylinder and a corresponding form, the scanning beam and theelectron beam may oscillate in one plane and the original and theprinting form be advanced linewise with respect thereto.

Embodiments of the invention are illustrated as examples in thedrawings:

FIG. l is a block circuit diagram of the complete installation whichschematically shows the construction of an apparatus for performing themethod according to the invention.

FIG. 2 is a similar view to FIG. 1, wherein the type of drive for theoriginal and the printing cylinder on the reception side are shownschematically.

FIG. 3 is a circuit diagram showing, the nature of the circuit at thereception station and the control pulse supply.

FIG. 4 shows schematically the electron-optical systern with the mostimportant components.

FIG. 5 is a greatly enlarged view of a cell made by the method accordingto the invention.

FIG. 6 shows a cell with a ridge due to melting, this cell being of thekind made by a known method.

FIGS. 7 and 8 are plan views of two axial contour shapes of cells.

In order to explain the invention, FIG. 1 shows in principle theconstruction of a plant for performing the method according to theinvention. The plant contains four essential main parts, the currentsupply part, the control part, the actual engraving device, and a vacuumpump station.

The electrical power supply part contains a highvoltage transformer Awhich produces the high-voltage of about 100,000 volts `required toproduce the electron beam. This transformer A contains an isolatingtransformer B which enables other high-potential electronic apparatus tobe operated, and a heating transformer C for vthe heater voltage for theelectron-optical system. To keep the individual values constant, thishigh-tension transformer A is advantageously connected in series with astabilizer D connected to the mains. Operation is carried out from aseparate control desk E.

The high-tension transformer A.C. leads to a device F, which Iisinsulated from earth and which will hereinafter be referred to as apotential tank, and which contains the electronic means required tocontrol the beam. By means of control knobs G the corresponding valuescan be set to Ithe required magnitudes from earth potcntial, `forexample the pulse duration and the pulse magnitude, and the receiver beset to the pulses coming from the scanning device L. Cables lead fromthe potential tank F to the actual engraving device which consists ofthe beam generator system H, H1 and a device to accommodate a printingcylinder J. This arrangement is in a vacuum-tight tank which isevacuated to a pressure below 10-3 mm. mercury column by means of avacuum pump station K.

FIG. 2 is a construction similar to FIG. 1, in which like referenceshave been used. In addition to the various parts shown diagrammaticallyin FG. 1, it shows a scanning device L for an original M which iscoupled to a drive N which is in turn coupled to the printing cylinder Jand wherein there is at the same time a driving connection O throughgearwheels which slide the carrier of the printing cylinder I by way ofa worm and wormwheel P. The drive N is also coupled through R to a pulsegenerator S.

FIG. 3 shows a circuit diagram of the installation.

Ref. 1A denotes the high-voltage transformer followed by a rectifierchain 2 and smoothing resistance 3, the negative end of which isconnected to the cathode 4 of an electron-beam tube while the positiveend is connected to earth through a measuring resistance 5. A heatertransformer 6 serves to supply the hot-cathode 4. A pulse generator 7and a rectifier 8 are provided in the potential tank F to produce aiixed bias for a control grid 9 of the electron-beam tube, this biasbeing externally adjustable by way of a variable resistance 10. Thepulse generator 7 serves to produce the said square wave pulses whichopen and close the electron beam in the rhythm of the printing cylindermovement. Said pulse generator 7 is at high-voltage potential and can betriggered externally by means of a device (not shown). Another device 11for the production of a D.C. voltage Serves to produce a fixed negativebias for the Wehnelt cylinder 12 of the electronbeam tube, and this biascan also be adjusted by means of a variable resistance 13. An A C.voltage can be applied to the Wehnelt cylinder by way of a workingresistance 14 and a circuit not shown in detail here, and this voltageis indicated at Mrz and serves to control the electron-beam intensityaccording to the brightness values of the original to be reproduced.This alternating voltage 14a accordingly fluctuates in the rhythm of thelightdark values of the original.

Au isolating transformer (not shown) is connected to the terminals 15Band serves to feed the pulse generator 7 and the two auxiliary voltagegenerating sources 8 and 11 and enables the conventional supply voltageof 220 v. A.C. to be coupled to the high-tension potential. The anode 16of the electron gun is at earth potential and hence at plus kv. withrespect to the cathode 4.

FIG. 4 shows the electron-optical system for producing the beam. Theactual engraving device consists of a vacuum-tight housing 20, the topend of which is sealed by a high-voltage insulator 21, with high-voltageleads 22. Inside the housing 20 is the hot-cathode 4 surrounded by theWehnelt cylinder 12. The control grid 9 serves for the light-darkmodulation of the electron beam. The electrons emerging from the cathode4 are accelerated by the anode 16. The electron beam 24 can be directedby means of an adjusting device 23 on to a mask 25 which masks out theinoperative part of the electron beam. An electron-beam image of theaperture 25 is produced on a printing cylinder 27 by means of a magneticlens 26 and thus an engraving is produced which is denoted generally byreference 2d.

The electrons emerging from the cathode 4 are combined by the controlgrid 9 and the Wehnelt cylinder 12 to form a beam which is acceleratedtowards the printing cylinder 27 by means of the anode 16. An energydistribution governed by the system prevails in the electron beam andits inoperative edges are cut off by the mask Z5. The remaining part ofthe beam contains only the energyridge electrons which by means of themagnetic lens 26 are projected on to the printing cylinder Z7 to give a'reduced image of the aperture 25. The electrons impinging upon thecylinder result in very intensive heating of the material at the pointof impact, and this material thus vaporises spontaneously. A depressionof predetermined size and depth is thus left on the printing cylinderaccording to the duration and energy of the electron beam.

The electron beam is opened only for short periods at a time by means ofthe control grid 9 and the pulse generator 7 while the voltage at theWehnelt cylinder 12, which voltage is controlled by the brightness ofthe original by means of the resistance 14, determines the intensity ofthe electron beam during the opening period. Cells of the required depthand size are thus produced in the printing form, block or plate independence on the intensity of the electron beam or the electron beampulses.

By means of a mechanical drive (not shown) the printing cylinder rotatesabout its lonigtudinal axis and is displaced along this longitudinalaxis. The depressions produced by the electron beam are thus situatedalong a spiral line of predetermined pitch on the cylinder,

FIG. 5 shows how a cell according to the invention appears in thecompleted state. It will be seen that it has somewhat beveled anks andthat there is no crater formation.

FIG. 6 shows the appearance of a cell with known processes. The craterformation is avoided in the invention by the fact that the inoperativeedges of the electron beam are cut olf by the mask.

FIGS. 7 and 8 show how any required shaping of the cells can be obtainedby suitable shape of the mask.

FIG. 7 is a plan view of a substantially square cell while FIG. 8 showsa diamond-shaped cell.

In addition to the above-explained advantages, the in- Vention has theadvantage that the centre axes of the individual cells are substantiallyperpendicular to the surface of the original both in the case of planeand in the case of, for example, cylindrically shaped originals orforms, blocks or plates. This is due to the fact that with the methodaccording to the invention a stationary electron beam and a movingorigin-al are used. This in turn has the advantage that apart from asynchronism of the movement between the original and the form, block orplate no synchronising devices whatever are required between thescanning device and the elect-ron-optic-al system.

As a result of the variable focussing, the sharpness of the dot edgesand the slope of the Hanks of the cells may be given an optimum value bymeans of the invention while the quality of the printed matter isimproved since the depth of the cells on the forms, blocks or plates andthe smoothness of their surfaces are controllable as required and asmost suitable.

I claim:

1. Apparatus for producing an engraved printing form comprising incombination:

an electron beam generator for projecting on a given plane a sharplyfocused beam of electrons,

first mounting means for supporting and positioning an electron beamengravable medium in said plane in the path of said beam,

a housing enclosing both said generator and said first mounting means,means coupled thereto for producing a vacuum within said housing alongthe entire path of said beam,

means for causing said electron beam to traverse the surface of saidengravable medium in accordance with a pattern which is identical and inabsolute synchronism with a predetermined scanning pattern of anoriginal,

means for coupling to said beam generator for controlling the intensityof the Ibeam a signal representative of the brightness values of saidoriginal along said scanning pattern,

and means directly synchronized with the traverse of the beam over thesurface of the engravable medium for periodically suppressing theengraving action of said beam to provide the characteristic dot patternof a printing form.

2. Apparatus for producing an engraved printing form comprising incombination:

an electron beam generator for projecting on a given plane a sharplyfocused bea-m of electrons,

first mounting means for supporting and positioning an electron beamengravable medium in said plane in the path of said beam,

a housing enclosing both said generator and said first mounting means,

means coupled thereto for producing a vacuum within said housing alongthe entire path of said beam, second mounting means for supporting anoriginal,

an electro-optical device associated with said second mounting means forscanning the surface of said original in accordance with a predeterminedscanning pattern, and for providing a voltage signal as a function ofthe brightness values thereof,

means for causing said electron beam to traverse the surface of saidengravable medium in accordance with a pattern which is identical and inabsolute synchronism with said predetermined scanning .pattern,

means coupling said signal output of said electro-optical device to saidibeam generator for controlling the intensity of the beam as a functionof said voltage signal,

and means directly synchronized with the traverse of the beam over thesurface of the engravable medium for periodically suppressing theengraving action of said beam to provide the' characteristic dot patternof a .printing form.

3. Apparatus for producing an intaglio printing form comprising incombination:

an electron beam generator for projecting on a given plane a sharplyfocused stationary beam of electrons,

rst mounting means for supporting and positioning an electron beamengravable medium in said plane in the path of said beam,

a housing enclosing both said generator and said first mounting means,

means coupled thereto for producing a vacuum within said housing alongthe entire path of said beam,

second mounting means for supporting an original,

an electro-optical device associated with said second mounting means forscanning the surface of said original in accordance with a predeterminedscanning pattern and for providing a voltage signal as a function of thebrightness values thereof,

means coupled to said first mounting means to impart driven motionthereto for causing said stationary electron beam to traverse thesurface of said engravable medium in accordance Iwith a pattern which isidentical and in absolute synchronism with said predetermined scanningpattern,

means coupling said signal output of said electro-optical device to saidbeam generator for controlling the intensity of the beam as a functionof said voltage signal,

and means directly synchronized with the traverse of the beam over thesurface of the engravable medium for periodically suppressing theengraving action of said beam to provide the characteristic dot patternof an intaglio form.

4. Apparatus for Iproducing an intaglio printing form comprising incombination:

an electron beam generator for projecting on a given plane a sharplyfocused stationary beam of electrons,

first mounting means for supporting and positioning an electron beamengravable medium in said plane in the path of said beam,

a housing enclosing both said generator and said first mounting means,

means coupled thereto for producing a vacuum within said housing alongthe entire path of said beam,

second mounting means for supporting an original,

an electro-optical device associated with said second mounting means forscanning the surface of said original in accordance with thepredetermined scanning pattern and for providing a voltage signal as afunction of the brightness values thereof,

means coupled to said first mounting means to impart driven motionthereto for causing said stationary electron beam to traverse thesurface of said engravable medium in accordance with a pattern which isidentical and in absolute synchronism with said predetermined scanningpattern,

means coupling said signal output of said electro-optical device to saidIbeam generator for controlling the intensity of the beam as a functionof said voltage signal,

and an electro-mechanical signal generator having a driven elementfixedly joined to said first mounting means for conjoint movement andhaving an output means coupled to said beam generator for periodicallysuppressing the engraving action of said beam in exact synchronism withthe traverse of the beam over the surface of the engravable medium toprovide the characteristic dot pattern of an intaglio form.

5. Apparatus according to claim 4, wherein the output means of saidelectro-mechanical signal generator comprises a photo-electric devicehaving an output coupled to said beam generator, and wherein said drivenelement comprises means for pulse modulating the intensity of theillumination to which said photo-electric device is responsive.

6. Apparatus according to claim 5, wherein said rst ymounting meanscomprises a cylindrical support mounted for rotation on a shaft, andwherein said pulse modulating means includes a light modulating discsecured to said shaft for rotation therewith, rotation of said disceffecting the modulation of said illumination.

7. Apparatus for producing an intaglio printing form comprising incombination:

an electron beam generator for projecting on a given plane a beam ofelectrons, said generator including a source of electrons, an aperturedmask, means for accelerating a stream of said electrons along aconverging path toward the aperture in said mask, and an electronic lenssystem positioned on the side of said mask which is remote from saidsource for focusing the electrons passing through said mask upon saidplane in a sharply defined image of the aperture in the mask,

first mounting means for supporting and positioning an elcctron beamengravable medium in said plane in the path of said beam,

a housing enclosing both said generator and said first mounting means,

means coupled thereto for producing a vacuum within said housing alongthe entire path of said beam, second mounting means for supporting anoriginal,

an electro-optical device associated with said second mounting means forscanning the surface of said original in accordance with a predeterminedscanning pattern and for providing a voltage signal as a function of thebrightness values thereof,

means for causing said electron beam to traverse the surface of saidengravable medium in accordance with a pattern which is identical and inabsolute `synchronism with said predetermined scanning pattern,

means coupling said signal output of said electro-optical device to saidbeam generator for controlling the intensity of the beam as a functionof said voltage signal,

and means directly synchronized with the traverse of the beam over thesurface of the engravable medium for periodically suppressing theengraving action of said beam to provide the characteristic dot patternof an intaglio form.

8. Apparatus for producing an intaglio printing form comprising incombination:

an electron beam generator for projecting on a given plane a beam ofelectrons, said generator including a source of electrons, an aperturedmask, means for accelerating a stream of said electrons along aconverging path toward the aperture in said mask, and an electronic lenssystem positioned on the side of Cil said mask which is remote from saidsource for focusing the electrons passing through said mask upon saidplane in a sharply dened image of the aperture in the mask,

first mounting means for supporting and positioning an electron beamengravable medium in said plane in the path of said beam,

a housing enclosing both said generator and said first mounting means,

means coupled thereto for producing a vacuum within i said housing alongthe entire path of said beam,

second mounting means for supporting an original, an electro-opticaldevice associated with said second mounting means for scanning thesurface of said original in accordance with a predetermined scanningpattern and for providing a voltage signal as a function of thebrightness Values thereof,

means coupled to said tirst mounting means to impart driven motionthereto for causing said stationary electron beam to traverse thesurface of said engravable medium in accordance with a pattern which isidentical and in absolute synchronism with said predetermined scanningpattern,

means coupling said signal output of said electro-optical device to saidbeam generator for controlling the intensity of the beam as a functionof said voltage signal,

and an electro-mechanical signal generator having a driven elementfixedly joined to said rst mounting means for conjoint movement andhaving an output means coupled to said beam generator for periodicallysuppressing the engraving action of said beam in exact synchronism withthe traverse of the beam over the surface of the engravable medium toprovide the characteristic dot pattern of an intaglio form.

9. Apparatus according to claim 8, wherein the output means of saidelectro-mechanical signal generator comprises a photo-electric devicehaving an output coupled to said beam generator, and wherein said drivenelement comprises means for Ipulse modulating the intensity of theillumination to which said photo-electric device is responsive.

10. Apparatus according to claim 9, wherein said first mounting meanscomprises a cylindrical support mounted for rotation on a shaft, andwherein said pulse modulating means includes a light modulating discsecured to said shaft for rotation therewith, rotation of said disceffecting the modulation of said illumination.

References Cited by the Examiner UNITED STATES PATENTS 2,164,297 6/1939Bedford. 2,195,489 4/1940 Iams 178-72 2,761,007 8/1956 ,Fisher et al.178-5.2 2,909,598 10/1959 Litferth 178-6.6 2,923,590 2/1960 Lorenz346-110 DAVID G. REDINBAUGH, Primary Examiner.

ROY LAKE, Examiner.

1. APPARATUS FOR PRODUCING AN ENGRAVED PRINTING FORM COMPRISING INCOMBINATION: AN ELECTRON BEAM GENERATOR FOR PROJECTING ON A GIVEN PLANEA SHARPLY FOCUSED BEAM OF ELECTRONS, FIRST MOUNTING MEANS FOR SUPPORTINGAND POSITIONING AN ELECTRON BEAM ENGRAVABLE MEDIUM IN SAID PLANE IN THEPATH OF SAID BEAM, A HOUSING ENCLOSING BOTH SAID GENERATOR AND SAIDFIRST MOUNTING MEANS, MEANS COUPLED THERETO FOR PRODUCING A VACUUMWITHIN SAID HOUSING ALONG THE ENTIRE PATH OF SAID BEAM MEANS FOR CAUSINGSAID ELECTRON BEAM TO TRAVERSE THE SURFACE OF SAID ENGRAVABLE MEDIUM INACCORDANCE WITH A PATTERN WHICH IS IDENTICAL AND IN ABSOLUTE SYNCHRONISMWITH A PREDETERMINED SCANNING PATTERN OF AN ORIGINAL, MEANS FOR COUPLINGTO SAID BEAM GENERATOR FOR CONTROLLING THE INTENSITY OF THE BEAM ASIGNAL REPRESENTATIVE OF THE BRIGHTNESS VALUES OF SAID ORIGINAL ALONGSAID SCANNING PATTERN, AND MEANS DIRECTLY SYNCHRONIZED WITH THETRANSVERSE OF THE BEAM OVER THE SURFACE OF THE ENGRAVING MEDIUM FORPERIODICALLY SUPPRESSING THE ENGRAVING ACTION OF SAID BEAM TO PROVIDETHE CHARACTERISTIC DOT PATTERN OF A PRINTING FORM.